Poly(lactic acid) (PLA) and poly(lactic-co-glycolic acid) (PLGA) have been widely applied as polymeric scaffolds in a wide range of biomedical applications, including tissue engineering, drug delivery, bioresorbable sutures and as implantable devices in dentistry.1 PL(G)A-based polymers offer particular benefits in terms of engineering a variety of controlled release vehicles, with drug-loaded sutures,2 microspheres,3 nanoparticles,1b stents4 and as blends within hydrogel networks5 all having been reported (some of which are used clinically). The widespread use of PL(G)A stems from the non-toxicity of the polymer, the safety and potential for clearance of its degradation products, its processibility, and its largely favorable mechanical properties for implantable devices.6 Moreover, tunable chemical stability of the polymer can be achieved by controlling the ratio of lactic acid and glycolic acid repeat units in the backbone, enabling the preparation of materials with tailored degradation profiles and thus drug release profiles.1b,6 
Owing to its relatively hydrophobic nature, PL(G)A has also been used as a degradable and cytocompatible hydrophobic block for the formation of amphiphilic block copolymers that can subsequently be self-assembled into nanoparticle (NP) formulations for drug delivery. Block copolymers of PL(G)A and poly(ethylene glycol) (PEG), both blocks of which have regulatory approval in a range of biomedical applications, have been particularly investigated as a promising precursor for NP formulations,7 exploiting the hydrophobicity of PL(G)A to drive assembly and effectively load (and thus deliver) drugs with poor water solubility, the tunable degradability of PL(G)A to control release of that drug (at least within the window of potential degradation times and drug-polymer affinities facilitated by the PL(G)A chemistry), and the protein-repellency of PEG to avoid non-specific uptake and promote long circulation times in vivo.8 End group functionalization of the PEG chains has also been used for the attachment of ligands to enable targeting of disease9. Using this strategy, it is possible to achieve higher uptake within the site of disease and/or target tissues that might otherwise be inaccessible.
However, while PL(G)A-PEG has been used successfully in drug delivery applications, the chemical nature of the polymer inherently limits its potential for functionalization. Given that both polymer blocks are made via ring-opening polymerization, reactive functional groups available for any post-functionalization strategy are only present at chain ends, limiting (for example) the ligand grafting density (often key to optimize to promote cooperative cell responses to those ligands10), the potential to engineer the affinity of the drug for the scaffold, and/or the potential to post-stabilize a self-assembled nanoparticle with covalent cross-links11. More recent development of functional ring-opening monomers has partially addressed this limitation, but such monomers still suffer from low conversions and the need to use protecting group chemistry to preserve the desired functional group during the polymerization process. Similarly, based on these same challenges inherent in including other functional monomers in ring-opening polymerizations, degradation of PL(G)A can only be tuned within a defined time window based on the L:G ratio and the interfacial properties (including potential smart properties) of the PEG phase are limited.